1. Field of the Invention
The invention relates to a device for the mechanical pressing of rounded book blocks and, more particularly, a device for the mechanical pressing of book blocks including a molding tool that applies a variable pressing force to the back of a book block.
2. Description of Related Art
In industrial book production, a book block with a rounded back receives the desired back shape corresponding to the cover type in the pressing processing station. The back shape being determined by a deep or flat fold. The pressing is effected by a molding tool, which is reciprocated over the entire width of the back of the book block and comprises a concave active surface, so that by applying pressure and friction, the folded printed sheets are bent over on both sides from the center of the book block back, namely at an angle increasing towards the outside. In this manner, the book block receives its mushroom-like shape and at the same time a back stabilization. In order to effect the pressing procedure, the book block is clamped between pressing strips with a defined overhang of the rounding end.
In European Patent 0,676,303, which is assigned to the present assignee hereof, in addition to a number of embodiments, a device for the mechanical pressing of book blocks of the construction described above is disclosed. By displacing the bearing with the carriage and the molding tool between the fixed lateral guides, the lateral deflection of the bearing is dispensed with. The axis of rotation of the molding tool lies at a defined distance below its point of contact with the back of the book block. The molding tool moves tangentially and overlies the pivoting axis. By means of stop screws in an intermediate support, the displacement is limited and in this manner the sliding movement is introduced into the lateral region in order to fold over the printed sheets. The size of the displacement stroke can be adjusted by varying the distance of the axis of rotation of the molding tool from the book block back and via the stop screws.